Integrated damage management reduces grazing of wild rice by resident Canada geese in New Jersey

Abstract

Tidal freshwater marshes of the Maurice River, New Jersey, USA, have been long renowned for robust stands of wild rice (Zizania aquatica). During the 1990s, these marshes experienced an apparent decline in wild rice. During 2000-2002, I used paired fenced exclosures and open control plots to measure herbivory by the Atlantic Flyway Resident Population of Canada geese (Branta canadensis) on wild rice and response of rice to an integrated damage management program (IDMP). The IDMP consisted of rendering goose nests unhatchable, shooting, and culling molting geese. The IDMP reduced the number of goslings by 60% during the first year and essentially eliminated recruitment during the second year. Prior to the IDMP, grazing by geese reduced the density of rice by 78% and the height of plants surviving grazing by 17%. With implementation of an IDMP, rice density between exclosures and control plots did not differ. Wetland managers should consider the grazing impacts that resident population Canada geese can incur on native plant communities and develop a plan for mitigating that damage. Ó 2014 The Wildlife Society.

Ten years of resident Canada goose damage management in a New Jersey tidal freshwater wetland

“…Nichols () noted that without an IDMP, the number of geese peaked on the study area in late June during the goose remige molt. This was caused by gosling recruitment and the apparent immigration of additional adult geese to molt in the denuded, lawn‐like landscape preferred by flightless, molting geese (Smith et al ).…”

“…In contrast, geese left the marsh in early June just prior to the molt during all IDMP years, presumably because maturing rice plants were unfavorable as forage and created a visual barrier generally avoided by molting geese. With no IDMP, goose density reached 0.60 geese/ha of marsh during the remige molt in late June (Nichols ), while during IDMP years the density of molting geese declined 90% to 0.06 geese/ha. The mean number of nests declined 70% from 2001–2003 to 2007–2010.…”

“…aquatica ; Oelke et al ). Ferren () described the vegetation characteristics and Nichols () further described the study area. Typical tidal amplitudes ranged from 1.3 m to 1.8 m. As a result of previous agricultural practices, the study area contained about 7.3 km of linear dike remnants of various lengths, many of which now occur as islands and provide nesting sites for geese (Fig.…”

“…The Maurice River estuary is an important site for wintering waterfowl and raptors (Sutton and Kerlinger , Sutton et al ). Excessive herbivory by Atlantic Flyway Resident Population Canada geese ( Branta canadensis ) has been responsible for dramatic declines of rice within marshes of the Patuxent River, Maryland, USA (Haramis and Kearns ) and Maurice River study site (Nichols ). However, in both studies, management programs abated grazing impacts by resident geese.…”

“…Breeding ospreys have been shown to be sensitive to disturbance (Swenson , Levenson and Koplin ). Given the aggressive nature of the integrated damage management program (IDMP) implemented for Canada geese on this study area (Nichols ), which involved shooting and boats operating outside of the main river channel during the spring breeding season, managers had a legitimate concern regarding potential impacts to ospreys. My goal was to restore the vegetation characteristics of this freshwater tidal marsh by reducing the number of geese over time while minimizing negative impacts to breeding ospreys.…”